The present invention relates to a gate valve. More particularly, the invention relates to a gate valve which comprises a compact assembly of easy to manufacture components that can be readily miniaturized to produce a small yet reliable flow control device.
Prior art gate valves, especially those used in the oil and gas industry, typically comprise a valve body, a flow passage which extends through the body between an inlet port and an outlet port, a gate cavity which extends partially through the body generally transverse to the flow passage, and a gate which is slidably disposed between a pair of seats that are mounted in the flow passage. Each seat includes a through bore which aligns with the flow passage, and the gate comprises a transverse hole which aligns with the through bores when the gate valve is in the open condition. The gate is connected to a valve stem which is rotationally supported in a bonnet that is connected to the valve body over the gate cavity. In operation, the valve stem is rotated to raise or lower the gate and bring the hole into or out of alignment with the through bores to thereby either open or close the flow passage, respectively.
These prior art gate valves typically comprise a large number of parts which are relatively difficult to manufacture and time consuming to assemble. Moreover, while gate valves are usually robust closure members, their large number of parts makes servicing these valves somewhat difficult. In addition, prior art gate valves are generally too large to be used in certain components which have relatively small volumes or cross sectional areas, such as the tubing hanger or tree cap components of flow completion assemblies for producing oil or gas from subsea wells.
Therefore, a need exists for a simplified gate valve which is simple to manufacture and which is small enough to be used in certain flow completion system components which have limited space for such valves.
In accordance with the present invention, these and other disadvantages in the prior art are overcome by providing a gate valve which comprises an elongated body which comprises first and second ends, a hole which extends longitudinally between the first and second ends, a first opening which communicates with the hole proximate the first end, a second opening which communicates with the hole proximate the second end, and a bore which extends transversely through the body and intersects the hole; first and second seats which are mounted in respective ends of the bore and which each include a passageway that aligns with the bore; a valve stem which is slidably positioned in the hole and which includes first and second piston portions that are separated by a gate portion, the stem being movable between an open position in which a hole in the gate portion is aligned with the passageways and a closed position in which the hole is offset from the passageways; and first and second means for sealing the first and second piston portions, respectively, against the hole. With this configuration, hydraulic pressure in a first piston chamber defined by the first piston portion, the first sealing means and the hole will move the gate from the open position to the closed position, and hydraulic pressure in a second piston chamber defined by the second piston portion, the second sealing means and the hole will move the gate from the closed position to the open position.
Thus, it may be seen that the gate valve of the present invention comprises a simple, modular construction. In addition, since the components of the gate valve are relatively uncomplicated, they may be easily scaled down to produce a gate valve which is sufficiently small to be used in several flow completion system components in which space is limited. Thus, the gate valve may be particularly advantageous for such flow completion system components as tree caps, controls bridges, tubing hangers or downhole devices.